/*  spng - simple-png utilities
 *
 *  Copyright (C) 2011  Yaacov Zamir <kobi.zamir@gamil.com>
 *  
 *  This program is free software: you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation, either version 3 of the License, or
 *  (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
 
#include <string.h>
#include <stdio.h>

/*
 * Table of CRC-32's of all single-byte values
 *  taken from ? 
 *  (TODO: find origin of table and add a note about it)
 */
const unsigned long crc_table[256] = {
    0x00000000L, 0x77073096L, 0xee0e612cL, 0x990951baL, 0x076dc419L,
    0x706af48fL, 0xe963a535L, 0x9e6495a3L, 0x0edb8832L, 0x79dcb8a4L,
    0xe0d5e91eL, 0x97d2d988L, 0x09b64c2bL, 0x7eb17cbdL, 0xe7b82d07L,
    0x90bf1d91L, 0x1db71064L, 0x6ab020f2L, 0xf3b97148L, 0x84be41deL,
    0x1adad47dL, 0x6ddde4ebL, 0xf4d4b551L, 0x83d385c7L, 0x136c9856L,
    0x646ba8c0L, 0xfd62f97aL, 0x8a65c9ecL, 0x14015c4fL, 0x63066cd9L,
    0xfa0f3d63L, 0x8d080df5L, 0x3b6e20c8L, 0x4c69105eL, 0xd56041e4L,
    0xa2677172L, 0x3c03e4d1L, 0x4b04d447L, 0xd20d85fdL, 0xa50ab56bL,
    0x35b5a8faL, 0x42b2986cL, 0xdbbbc9d6L, 0xacbcf940L, 0x32d86ce3L,
    0x45df5c75L, 0xdcd60dcfL, 0xabd13d59L, 0x26d930acL, 0x51de003aL,
    0xc8d75180L, 0xbfd06116L, 0x21b4f4b5L, 0x56b3c423L, 0xcfba9599L,
    0xb8bda50fL, 0x2802b89eL, 0x5f058808L, 0xc60cd9b2L, 0xb10be924L,
    0x2f6f7c87L, 0x58684c11L, 0xc1611dabL, 0xb6662d3dL, 0x76dc4190L,
    0x01db7106L, 0x98d220bcL, 0xefd5102aL, 0x71b18589L, 0x06b6b51fL,
    0x9fbfe4a5L, 0xe8b8d433L, 0x7807c9a2L, 0x0f00f934L, 0x9609a88eL,
    0xe10e9818L, 0x7f6a0dbbL, 0x086d3d2dL, 0x91646c97L, 0xe6635c01L,
    0x6b6b51f4L, 0x1c6c6162L, 0x856530d8L, 0xf262004eL, 0x6c0695edL,
    0x1b01a57bL, 0x8208f4c1L, 0xf50fc457L, 0x65b0d9c6L, 0x12b7e950L,
    0x8bbeb8eaL, 0xfcb9887cL, 0x62dd1ddfL, 0x15da2d49L, 0x8cd37cf3L,
    0xfbd44c65L, 0x4db26158L, 0x3ab551ceL, 0xa3bc0074L, 0xd4bb30e2L,
    0x4adfa541L, 0x3dd895d7L, 0xa4d1c46dL, 0xd3d6f4fbL, 0x4369e96aL,
    0x346ed9fcL, 0xad678846L, 0xda60b8d0L, 0x44042d73L, 0x33031de5L,
    0xaa0a4c5fL, 0xdd0d7cc9L, 0x5005713cL, 0x270241aaL, 0xbe0b1010L,
    0xc90c2086L, 0x5768b525L, 0x206f85b3L, 0xb966d409L, 0xce61e49fL,
    0x5edef90eL, 0x29d9c998L, 0xb0d09822L, 0xc7d7a8b4L, 0x59b33d17L,
    0x2eb40d81L, 0xb7bd5c3bL, 0xc0ba6cadL, 0xedb88320L, 0x9abfb3b6L,
    0x03b6e20cL, 0x74b1d29aL, 0xead54739L, 0x9dd277afL, 0x04db2615L,
    0x73dc1683L, 0xe3630b12L, 0x94643b84L, 0x0d6d6a3eL, 0x7a6a5aa8L,
    0xe40ecf0bL, 0x9309ff9dL, 0x0a00ae27L, 0x7d079eb1L, 0xf00f9344L,
    0x8708a3d2L, 0x1e01f268L, 0x6906c2feL, 0xf762575dL, 0x806567cbL,
    0x196c3671L, 0x6e6b06e7L, 0xfed41b76L, 0x89d32be0L, 0x10da7a5aL,
    0x67dd4accL, 0xf9b9df6fL, 0x8ebeeff9L, 0x17b7be43L, 0x60b08ed5L,
    0xd6d6a3e8L, 0xa1d1937eL, 0x38d8c2c4L, 0x4fdff252L, 0xd1bb67f1L,
    0xa6bc5767L, 0x3fb506ddL, 0x48b2364bL, 0xd80d2bdaL, 0xaf0a1b4cL,
    0x36034af6L, 0x41047a60L, 0xdf60efc3L, 0xa867df55L, 0x316e8eefL,
    0x4669be79L, 0xcb61b38cL, 0xbc66831aL, 0x256fd2a0L, 0x5268e236L,
    0xcc0c7795L, 0xbb0b4703L, 0x220216b9L, 0x5505262fL, 0xc5ba3bbeL,
    0xb2bd0b28L, 0x2bb45a92L, 0x5cb36a04L, 0xc2d7ffa7L, 0xb5d0cf31L,
    0x2cd99e8bL, 0x5bdeae1dL, 0x9b64c2b0L, 0xec63f226L, 0x756aa39cL,
    0x026d930aL, 0x9c0906a9L, 0xeb0e363fL, 0x72076785L, 0x05005713L,
    0x95bf4a82L, 0xe2b87a14L, 0x7bb12baeL, 0x0cb61b38L, 0x92d28e9bL,
    0xe5d5be0dL, 0x7cdcefb7L, 0x0bdbdf21L, 0x86d3d2d4L, 0xf1d4e242L,
    0x68ddb3f8L, 0x1fda836eL, 0x81be16cdL, 0xf6b9265bL, 0x6fb077e1L,
    0x18b74777L, 0x88085ae6L, 0xff0f6a70L, 0x66063bcaL, 0x11010b5cL,
    0x8f659effL, 0xf862ae69L, 0x616bffd3L, 0x166ccf45L, 0xa00ae278L,
    0xd70dd2eeL, 0x4e048354L, 0x3903b3c2L, 0xa7672661L, 0xd06016f7L,
    0x4969474dL, 0x3e6e77dbL, 0xaed16a4aL, 0xd9d65adcL, 0x40df0b66L,
    0x37d83bf0L, 0xa9bcae53L, 0xdebb9ec5L, 0x47b2cf7fL, 0x30b5ffe9L,
    0xbdbdf21cL, 0xcabac28aL, 0x53b39330L, 0x24b4a3a6L, 0xbad03605L,
    0xcdd70693L, 0x54de5729L, 0x23d967bfL, 0xb3667a2eL, 0xc4614ab8L,
    0x5d681b02L, 0x2a6f2b94L, 0xb40bbe37L, 0xc30c8ea1L, 0x5a05df1bL,
    0x2d02ef8dL
};

unsigned long write(FILE * fp, unsigned char * c, unsigned long len) {
    // copy data to file 
    fwrite(c, 1, len, fp);

    return len;
}

void writelong(FILE * fp, int l)
{
    unsigned char *c;

    c = (unsigned char *)&l;
    write(fp, c+3, 1);
    write(fp, c+2, 1);
    write(fp, c+1, 1);
    write(fp, c+0, 1);
}

unsigned long writelongcrc(FILE * fp, unsigned long crc, int l)
{
    unsigned char *c;

    c = (unsigned char *)&l;
    write(fp, c+3, 1);
    write(fp, c+2, 1);
    write(fp, c+1, 1);
    write(fp, c+0, 1);

    crc = crc ^ 0xFFFFFFFFL;
    crc = crc_table[(crc ^ (*(c+3))) & 0xff] ^ (crc >> 8);
    crc = crc_table[(crc ^ (*(c+2))) & 0xff] ^ (crc >> 8);
    crc = crc_table[(crc ^ (*(c+1))) & 0xff] ^ (crc >> 8);
    crc = crc_table[(crc ^ (*(c+0))) & 0xff] ^ (crc >> 8);
    crc = crc ^ 0xFFFFFFFFL;

    return crc;
}

unsigned long Xwritelongcrc(FILE * fp, unsigned long crc, int l)
{
    unsigned char *c;

    c = (unsigned char *)&l;
    write(fp, c+0, 1);
    write(fp, c+1, 1);
    write(fp, c+2, 1);
    write(fp, c+3, 1);
    
    crc = crc ^ 0xFFFFFFFFL;
    crc = crc_table[(crc ^ (*(c+0))) & 0xff] ^ (crc >> 8);
    crc = crc_table[(crc ^ (*(c+1))) & 0xff] ^ (crc >> 8);
    crc = crc_table[(crc ^ (*(c+2))) & 0xff] ^ (crc >> 8);
    crc = crc_table[(crc ^ (*(c+3))) & 0xff] ^ (crc >> 8);
    crc = crc ^ 0xFFFFFFFFL;

    return crc;
}

unsigned long writewordcrc(FILE * fp, unsigned long crc, short s)
{
    unsigned char *c;

    c = (unsigned char *)&s;
    write(fp, c+1, 1);
    write(fp, c+0, 1);
    
    crc = crc ^ 0xFFFFFFFFL;
    crc = crc_table[(crc ^ (*(c+1))) & 0xff] ^ (crc >> 8);
    crc = crc_table[(crc ^ (*(c+0))) & 0xff] ^ (crc >> 8);
    crc = crc ^ 0xFFFFFFFFL;

    return crc;
}

unsigned long Xwritewordcrc(FILE * fp, unsigned long crc, short s)
{
    unsigned char *c;

    c = (unsigned char *)&s;
    write(fp, c+0, 1);
    write(fp, c+1, 1);
    
    crc = crc ^ 0xFFFFFFFFL;
    crc = crc_table[(crc ^ (*(c+0))) & 0xff] ^ (crc >> 8);
    crc = crc_table[(crc ^ (*(c+1))) & 0xff] ^ (crc >> 8);
    crc = crc ^ 0xFFFFFFFFL;

    return crc;
}

unsigned long writebytecrc(FILE * fp, unsigned long crc, unsigned char c)
{
    write(fp, &c, 1);
    
    crc = crc ^ 0xFFFFFFFFL;
    crc = crc_table[(crc ^ c) & 0xff] ^ (crc >> 8);
    crc = crc ^ 0xFFFFFFFFL;

    return crc;
}

unsigned long beginchunk(FILE * fp, unsigned long crc, char *name, int len)
{
    unsigned long l;

    l = len;
    writelong(fp, l);
    write(fp, (unsigned char *)name, 4);

    crc = 0xFFFFFFFFL;
    crc = crc_table[(crc ^ name[0]) & 0xff] ^ (crc >> 8);
    crc = crc_table[(crc ^ name[1]) & 0xff] ^ (crc >> 8);
    crc = crc_table[(crc ^ name[2]) & 0xff] ^ (crc >> 8);
    crc = crc_table[(crc ^ name[3]) & 0xff] ^ (crc >> 8);
    crc = crc ^ 0xFFFFFFFFL;

    return crc;
}

unsigned long endchunk(FILE * fp, unsigned long crc)
{
    writelong(fp, crc);

    return crc;
}

unsigned long update_crc(unsigned char * data, unsigned long len, 
    unsigned long crc) {
    unsigned long i;
    
    // update crc
    crc = crc ^ 0xFFFFFFFFL;
    for (i = 0; i < len; i++)
        crc = crc_table[(crc ^ data[i]) & 0xff] ^ (crc >> 8);
    crc = crc ^ 0xFFFFFFFFL;
    
    return crc;
}

int
write_png_magic(FILE *fp) {
    static const unsigned char png_magic[8] = {137, 80, 78, 71, 13, 10, 26, 10};
    
    // write png magic
    fwrite(png_magic, 1, 8, fp);
}

unsigned long
write_png_header(FILE *fp, unsigned long w, unsigned long h) {
    unsigned long crc;
    
    // reset crc
    crc = 0;

    // write header chank
    crc = beginchunk(fp, crc, "IHDR", 0x0d);
    crc = writelongcrc(fp, crc, w); /* width */
    crc = writelongcrc(fp, crc, h); /* height */
    crc = writebytecrc(fp, crc, 8); /* bit depth */
    crc = writebytecrc(fp, crc, 3); /* color type */
    crc = writebytecrc(fp, crc, 0); /* compression */
    crc = writebytecrc(fp, crc, 0); /* filter */
    crc = writebytecrc(fp, crc, 0); /* interlace */
    crc = endchunk(fp, crc);

    return crc;
}

unsigned long
write_png_palet(FILE *fp, unsigned long crc) {
    unsigned int i;
    
    // write palet chank
    crc = beginchunk(fp, crc, "PLTE", 256 * 3);
    for (i = 0; i < 256; i++) {
        crc = writebytecrc(fp, crc, (i & 0xc0));
        crc = writebytecrc(fp, crc, (i & 0x38) << 2);
        crc = writebytecrc(fp, crc, (i & 0x07) << 5);
    }
    crc = endchunk(fp, crc);

    return crc;
}

unsigned long
write_png_data(FILE *fp, unsigned long crc, unsigned long adler_crc,
    unsigned char * data, unsigned long len) {
     
    // write png data
    crc = beginchunk(fp, crc, "IDAT", 2 + len + 4);
    // compression method
    crc = writewordcrc(fp, crc, ((0x0800 + 30) / 31) * 31 ); 

    fwrite(data, 1, len, fp);
    crc = update_crc(data, len, crc);
    
    // finish zip part (adler crc)
    crc = writelongcrc(fp, crc, adler_crc);

    // close data chank - write crc
    crc = endchunk(fp, crc);
    
    return crc;
}

unsigned long
write_png_end(FILE *fp, unsigned long crc) {
    
    // write end chank
    crc = beginchunk(fp, crc, "IEND", 0);
    crc = endchunk(fp, crc);
    
    return crc;
}

